Construction materials that are widely used as house appliances and interior materials such as furniture, a top panel of a desk, various kinds of counters, and doors generally include decorative boards obtained by shaping synthetic resin materials, for example, melamine resin decorative boards.
Conventionally, thermosetting resin decorative boards each having a concavoconvex pattern on the surface thereof include those having formed thereon a concavoconvex pattern using an emboss mold or a concavoconvex resin sheet and those having formed thereon a concavoconvex pattern using a shaping sheet. However, when the emboss mold with a concavoconvex pattern is used, it is necessary to subject the mold to surface treatment such as blasting and etching, so there will be restrictions to the concavoconvex pattern and elaborateness of the design pattern. Further, when the thermosetting resin decorative board is produced, an expensive mold plate and a spare mold plate are needed, which increases labor and cost for the production of the decorative board, thus largely increasing the production cost and making the product expensive.
Further, in the case of the concavoconvex resin sheet, the thermosetting resin decorative board becomes difficult to be peeled after curing of the resin, and as a result, an aluminum foil, a polypropylene film, or the like must be inserted between the mold plate and the resin sheet. Accordingly, it is very difficult to form a fine concavoconvex pattern with sharpness.
Incidentally, with a recent consumer orientation toward high grade articles, a high-grade feeling is demanded for house appliances such as furniture, desks, various kinds of counters and doors, or interior materials and hence, decorative boards used therefor are demanded to have an appearance that afford a high-grade feeling. Accordingly, it has become important to impart texture to such articles and various methods of imparting a fine concavoconvex pattern to a decorative board have been proposed.
For example, a shaping sheet has been proposed which includes a base material sheet having formed on a surface thereof a concavoconvex pattern with an ionization radiation-curable resin, in which the shaping sheet has a crosslink density sufficient not to cause cracks of the concavoconvex pattern when the shaping sheet is peeled to enable reproduction of desired designed patterns faithfully and repeated use of the shaping sheet (cf., Patent Document 1, claims).
However, the above-mentioned shaping sheet has a limitation in the expression of the concavoconvex pattern when the concave portions are fine since when the shaping sheet is fabricated, the fabrication method includes a step of peeling the sheet from a rolled engraved plate.
Further, the above-mentioned method has the problem in that it cannot provide a clear concavoconvex pattern when concave portions are fine. On the other hand, when the concave portions are more or less wide, convex portions higher than the raised portions occur although the method can provide a concavoconvex design on the surface of the base material, and the method fails to provide a realistic feeling in the case of, for example, wood grain patters and unsatisfactory appearance and touch.
Further, a shaping sheet has been proposed which has formed on the surface thereof a concavoconvex layer made of a resin composition composed of an inorganic filler and a binder resin, in which only the resin composition for forming a fine concavoconvex layer that is applied onto a picture pattern formed by a repellent resin is rejected to form the concavoconvex layer (cf., Patent Document 2, claims).
However, since the concavoconvex layer is formed by rejecting the resin composition for forming the concavoconvex layer, the above-mentioned shaping sheet has poor stability of picture by a concavoconvex pattern and it takes an extremely long period of time for producing a shaping sheet because aging for a certain period of time for curing the concavoconvex layer is required. Therefore, the above-mentioned shaping sheet can not quickly respond to consumers' diversified needs.
Further, when used repeatedly, shaping sheets with a polyester film as a base material suffer from separation of impurities out of the base material to contaminate the surface of the shaping sheet, and because of the contamination, it often became difficult to shape a fine concavoconvex pattern with sharpness.
The decorative boards fabricated using the above-mentioned shaping sheets are widely used generally for resin decorative boards obtained by shaping synthetic resin materials, for example, polyester decorative boards.
Such a resin decorative board is known to be produced by a method of producing a decorative board having a concavoconvex surface that includes coating a substrate with a resin composition containing an unsaturated polyester resin or the like, superimposing a shaping sheet having a concavoconvex pattern on the resin, curing the resin composition, and peeling the shaping sheet having the concavoconvex pattern. As the shaping sheet used for producing a resin decorative board having a concavoconvex surface by such a method, a shaping sheet is proposed which has a wood grain concavoconvex picture on a surface thereof and a cured silicone resin over the whole surface thereof (cf., for example, Patent Document 3).
However, since the concavoconvex pattern imparted to the decorative board are not sufficiently fine and the strength of the surface is insufficient, it is difficult to repeatedly use the shaping sheet.
Further, as polyester decorative boards with highly elaborated design, those having well matched wood grain color patterns and a concavoconvex pattern have been proposed (cf., for example, Patent Document 4).
However, such polyester decorative boards have the problems in that the size of the picture varies as a result of contraction of the sheet since resins that cure at room temperature are used, so correction of the original printing plate is necessary.
Further, a pigment that imparts design properties, such as a pearl pigment, a silver pigment, and a titanium pigment is added to an article to be shaped, to thereby impart decorativeness to the decorative board. In this case, the design property-imparting pigment contained in the article to be shaped may be separated in the process of producing decorative boards, resulting in failure in decorativeness of the decorative board. Further, the separated design property-imparting pigment may remain on the surface of a mirror-finished metal plate or a shaping sheet, so the repeated shapability may be prevented.
[Patent Document 1]: JP 7-164519 A
[Patent Document 2]: JP 5-92484 A
[Patent Document 3]: JP 7-144398 A
[Patent Document 4]: JP 8-267687 A